<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <h3>实现三列宽度自适应布局</h3>
    <div id="left">我是左边</div>
    <div id="right">我是右边</div>
    <div id="center">我是中间</div>

    <h3>自身浮动布局</h3>
    <div id="left2">我是左边</div>
    <div id="right2">我是右边</div>
    <div id="center2">我是中间</div>

    <h3>使用margin负值法进行布局</h3>
    <div id="wrap">
      <div id="center"></div>
    </div>
    <div id="left_margin"></div>
    <div id="right_margin"></div>

    <h3>使用flex盒子进行布局</h3>
    <div id="flexbox">
      <div id="left"></div>
      <div id="center"></div>
      <div id="right"></div>
    </div>

    <style>
      #left {
        width: 200px;
        height: 200px;
        position: absolute;
        background-color: red;
        left: 0;
      }
      #right {
        width: 200px;
        height: 200px;
        position: absolute;
        background-color: red;
        right: 0;
      }
      #center {
        height: 200px;
        background-color: sandybrown;
        margin-left: 210px;
        margin-right: 210px;
      }
      #left2 {
        width: 200px;
        height: 150px;
        float: left;
        background-color: slategrey;
      }
      #right2 {
        width: 200px;
        height: 150px;
        float: right;
        background-color: slategrey;
      }
      #center2 {
        height: 150px;
        background-color: sandybrown;
        margin-left: 210px;
        margin-right: 210px;
      }
      #wrap {
        width: 100%;
        height: 100px;
        background-color: #fff;
        float: left;
      }
      #wrap #center {
        margin: 0 210px;
        height: 100px;
        background-color: #ffe6b8;
      }
      #left_margin,
      #right_margin {
        float: left;
        width: 200px;
        height: 100px;
        background-color: darkorange;
      }
      #left_margin {
        margin-left: -100%;
        background-color: lightpink;
      }
      #right_margin {
        margin-left: -200px;
      }
      
      #flexbox {
        width: 100%;
        display: flex;
        height: 100px;
        margin: 10px;
      }
      #flexbox #left,
      #flexbox #right {
        width: 200px;
        height: 100px;
        margin: 10px;
        background-color: lightpink;
      }
      #flexbox #center {
        flex: 1;
        height: 100px;
        margin: 10px;
        background-color: lightgreen;
      }
    </style>
  </body>
</html>
